DETAILED ACTION
Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Claim Rejections - 35 USC § 102
The following is a quotation of the appropriate paragraphs of 35 U.S.C. 102 that form the basis for the rejections under this section made in this Office action:
A person shall be entitled to a patent unless –
(a)(1) the claimed invention was patented, described in a printed publication, or in public use, on sale, or otherwise available to the public before the effective filing date of the claimed invention.
Claims 1 – 7, 9, 17, 18, 20, 21, 23 and 24 are rejected under 35 U.S.C. 102(a)(1) as being anticipated by Yamashita (US 2012/0205739).
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(Claim 1) Yamashita teaches an SiC semiconductor device comprising:
an SiC chip that has a main surface (top); and
an n-type drift region (3, 7b, 7c) that is formed as a layer extending along the main surface in a surface layer portion of the main surface, includes at least two types of pentavalent elements within the same layer, and has an impurity concentration adjusted by the at least two types of pentavalent elements (paragraphs 65, 67, 70, Nitrogen/Phosphorus/Antimony).
(Claim 2) Yamashita teaches wherein the drift region has an impurity concentration that is adjusted such as to increase toward the main surface (paragraphs 65, 67,70).
(Claim 3) Yamashita teaches wherein the drift region (3, 7b, 7c) has an impurity concentration adjusted by pentavalent elements other than phosphorus (paragraphs 65, 67, 70).
(Claim 4) Yamashita teaches wherein the drift region includes nitrogen as a pentavalent element and a pentavalent element other than nitrogen (paragraphs 65, 67, 70).
(Claim 5) Yamashita teaches wherein the drift region has a basal concentration (3) due to a first impurity that is a pentavalent element (paragraph 65) and an added concentration (7b, 7c) due to a second impurity that is a pentavalent element other than the first impurity (paragraphs 67, 70).
(Claim 6) Yamashita teaches wherein the first impurity is a pentavalent element other than phosphorus (paragraph 65), and the second impurity is a pentavalent element other than phosphorus (paragraphs 67, 70).
(Claim 7) Yamashita teaches wherein the first impurity is nitrogen (paragraph 65), and the second impurity is at least one among arsenic and antimony (paragraph 67, 70).
(Claim 9) Yamashita teaches wherein the basal concentration (3) has a concentration distribution that is substantially constant in a thickness direction.
(Claim 17) Yamashita teaches wherein the drift region (3) has a thickness belonging to any one range among not less than 1 micron and not more than 5 micron, not less than 5 micron and not more than 10 micron, not less than 10 micron and not more than 15 micron, not less than 15 micron and not more than 20 micron, and not less than 20 micron and not more than 25 micron (paragraph 65).
(Claim 18) Yamashita teaches wherein the SiC chip is constituted of an SiC monocrystal that is a hexagonal crystal, and the main surface is arranged along a c-plane of the SiC monocrystal and has an off angle of not more than 10° with respect to the c-plane (paragraph 65, SiC 4H; hexagonal Bravais lattice).
(Claim 20) Yamashita teaches wherein the drift region is formed in an SiC epitaxial layer (paragraph 45).
(Claim 21) Yamashita teaches wherein the drift region (3, 7b, 7c) includes a first region (3) that is formed as a layer extending along the main surface and includes one type of the pentavalent element (paragraph 65), and a second layer (7a, 7b) that is formed as a layer in a region between the main surface and the first region and includes the at least two types of pentavalent elements (paragraphs 67, 70).
(Claim 23) Yamashita teaches an SiC semiconductor device comprising:
an SiC chip that has a main surface (top); and
an n-type drift region (3, 7b, 7c, paragraph 45) that is formed in a surface layer portion of the main surface and has an impurity concentration adjusted by at least two types of pentavalent elements (paragraphs 51, 54, 57);
wherein the drift region (fig. 3F #3) has a basal concentration (n-) due to a first impurity that is a pentavalent element (paragraph 65) and an added concentration (n) due to a second impurity that is a pentavalent element other than the first impurity (paragraphs 67, 70).
(Claim 24) Yamashita teaches wherein the first impurity is a pentavalent element (paragraph 65, nitrogen) other than phosphorous and the second impurity is a pentavalent element (paragraph 70, antimony) other than phosphorus.
Claims 1, 2, 4, 17, 18 and 20 are rejected under 35 U.S.C. 102(a)(1) as being anticipated by Shiomi (US 2017/0133466).
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(Claim 1) Shiomi teaches an SiC semiconductor device comprising:
an SiC chip that has a main surface (top); and
an n-type drift region (12) that is formed as a layer extending along the main surface in a surface layer portion of the main surface, includes at least two types of pentavalent elements within the same layer, and has an impurity concentration adjusted by the at least two types of pentavalent elements (paragraph 93, Nitrogen/Phosphorus).
(Claim 2) Shiomi teaches wherein the drift region has an impurity concentration that is adjusted such as to increase toward the main surface (paragraphs 79, 80).
(Claim 4) Shiomi teaches wherein the drift region includes nitrogen as a pentavalent element and a pentavalent element other than nitrogen (paragraph 93).
(Claim 17) Shiomi teaches wherein the drift region (12 = 12a + 12b +12c) has a thickness belonging to any one range among not less than 1 micron and not more than 5 micron, not less than 5 micron and not more than 10 micron, not less than 10 micron and not more than 15 micron, not less than 15 micron and not more than 20 micron, and not less than 20 micron and not more than 25 micron (paragraphs 79, 80).
(Claim 18) Shiomi teaches wherein the SiC chip is constituted of an SiC monocrystal that is a hexagonal crystal, and the main surface is arranged along a c-plane of the SiC monocrystal and has an off angle of not more than 10° with respect to the c-plane (paragraph 63, SiC 4H; hexagonal Bravais lattice).
(Claim 20) Shiomi teaches wherein the drift region is formed in an SiC epitaxial layer (paragraph 54).
Claims 10, 12 – 14, 16 and 22 are rejected under 35 U.S.C. 102(a)(1) as being anticipated by Zhang et al. (US 2008/0105949).
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(Claim 10) Zhang et al. teach an SiC semiconductor device comprising:
an SiC chip (paragraph 40) that has a main surface (top); and
a p-type drift region (16/40) that is formed in a surface layer portion of the main surface and has an impurity (paragraph 42) concentration adjusted by a trivalent element (paragraphs 40 – 42, aluminum is the only disclosed element in the specification for p-type dopant) other than boron;
wherein the drift region (16/40) has an impurity concentration that is adjusted such as to increase toward the main surface (#16 is 2.times.10.sup.14 cm.sup.-3 to about 6.times.10.sup.14 cm.sup.-3, paragraph 40, #40 is 1.times.10.sup.16 cm.sup.-3 to about 5.times.10.sup.18 cm.sup.-3, paragraph 42).
(Claim 12) Zhang et al. teach wherein the drift region includes at least one type of trivalent element among aluminum, gallium, and indium (paragraph 42).
(Claim 13) Zhang et al. teach an SiC semiconductor device comprising:
an SiC chip (paragraph 40) that has a main surface (top); and
a p-type drift region (16/40) that is formed in a surface layer portion of the main surface and has an impurity (paragraphs 40, 42) concentration adjusted by a trivalent element other than boron (paragraphs 40, 42, aluminum);
wherein the drift region has a basal (#16) concentration due to a first impurity that is a trivalent element (paragraph 40) and an added concentration (#40) due to a second impurity that is a trivalent element being the same as or different from the first impurity (paragraph 42, aluminum).
(Claim 14) Zhang et al. teach wherein the first impurity is aluminum (paragraph 40), and the second impurity is at least one among aluminum, gallium, and indium (paragraph 42).
(Claim 16) Zhang et al. teach wherein the basal (16) concentration has a concentration distribution that is substantially constant in a thickness direction (paragraph 40).
(Claim 22) Zhang et al. teach wherein the drift region has a basal concentration (16) due to a first impurity that is a trivalent element and an added concentration (40) due to a second impurity that is a trivalent element being the same as or different from the first impurity (paragraphs 40, 42).
Claim Rejections - 35 USC § 103
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
The factual inquiries for establishing a background for determining obviousness under 35 U.S.C. 103 are summarized as follows:
1. Determining the scope and contents of the prior art.
2. Ascertaining the differences between the prior art and the claims at issue.
3. Resolving the level of ordinary skill in the pertinent art.
4. Considering objective evidence present in the application indicating obviousness or nonobviousness.
This application currently names joint inventors. In considering patentability of the claims the examiner presumes that the subject matter of the various claims was commonly owned as of the effective filing date of the claimed invention(s) absent any evidence to the contrary. Applicant is advised of the obligation under 37 CFR 1.56 to point out the inventor and effective filing dates of each claim that was not commonly owned as of the effective filing date of the later invention in order for the examiner to consider the applicability of 35 U.S.C. 102(b)(2)(C) for any potential 35 U.S.C. 102(a)(2) prior art against the later invention.
Claims 3 – 7 and 9 are rejected under 35 U.S.C. 103 as being unpatentable over Shiomi (US 2017/0133466) in view of Ng et al. (US 2013/0181285).
(Claim 3) Shiomi lacks wherein the drift region has an impurity concentration adjusted by pentavalent elements other than phosphorus.
However, Ng et al. teach wherein the drift region has an impurity concentration adjusted by pentavalent elements other than phosphorus (paragraph 13) as art recognized equivalents.
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to incorporate the references as art recognized equivalents.
(Claim 4) Shiomi lacks wherein the drift region includes nitrogen as a pentavalent element and pentavalent element other than nitrogen.
However, Ng et al. teach wherein the drift region includes nitrogen as a pentavalent element and pentavalent element other than nitrogen (paragraph 13) as art recognized equivalents.
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to incorporate the references as art recognized equivalents.
(Claim 5) Shiomi teaches wherein the drift region has a basal concentration (12c, paragraph 80, nitrogen) due to a first impurity that is a pentavalent element and an added concentration (12a, 12b, paragraph 79) due to a second impurity that is a pentavalent element. (other than the first impurity).
Shiomi lacks wherein the first and second impurities are different.
However, Ng et al. teach wherein the drift region has a basal concentration due to a first impurity that is a pentavalent element and an added concentration due to a second impurity that is a pentavalent element other than the first impurity (paragraph 13) as art recognized equivalents.
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to incorporate the references as art recognized equivalents.
(Claim 6) Shiomi lacks wherein the first impurity is a pentavalent element other than phosphorus, and the second impurity is a pentavalent element other than phosphorus.
However, Ng et al. teach wherein the first impurity is a pentavalent element other than phosphorus, and the second impurity is a pentavalent element other than phosphorus (paragraph 13) as art recognized equivalents.
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to incorporate the references as art recognized equivalents.
(Claim 7) Shiomi lacks wherein the first impurity is nitrogen, and the second impurity is at least one among arsenic and antimony.
However, Ng et al. teach wherein the first impurity is nitrogen, and the second impurity is at least one among arsenic and antimony (paragraph 13) as art recognized equivalents.
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to incorporate the references as art recognized equivalents.
(Claim 9) Shiomi teaches wherein the basal concentration (12c, paragraph 80) has a concentration distribution that is substantially constant in a thickness direction.
Claim 19 is rejected under 35 U.S.C. 103 as being unpatentable over Yamashita (US 2012/0205739) in view of Kawada et al. (US 2018/0061960).
(Clam 19) Yamashita lacks wherein the off angle has an off direction oriented along an a-axis direction of the SiC monocrystal.
However, Kawada et al. teach wherein the off angle has an off direction oriented along an a-axis direction of the SiC monocrystal (fig. 13A, paragraph 57) for the benefit of improving electron mobility (paragraph 58).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to incorporate the references for the benefit of improving electron mobility.
Claim 19 is rejected under 35 U.S.C. 103 as being unpatentable over Shiomi (US 2017/0133466) in view of Kawada et al. (US 2018/0061960).
(Clam 19) Shiomi lacks wherein the off angle has an off direction oriented along an a-axis direction of the SiC monocrystal.
However, Kawada et al. teach wherein the off angle has an off direction oriented along an a-axis direction of the SiC monocrystal (fig. 13A, paragraph 57) for the benefit of improving electron mobility (paragraph 58).
Therefore, it would have been obvious to one of ordinary skill in the art before the effective filing date of the claimed invention to incorporate the references for the benefit of improving electron mobility.
Allowable Subject Matter
Claims 8 and 15 are objected to as being dependent upon a rejected base claim, but would be allowable if rewritten in independent form including all of the limitations of the base claim and any intervening claims.
(Claims 8, 15) wherein the added concentration has a concentration distribution that increases toward the main surface.
Response to Arguments
Applicant's arguments filed on December 23, 2025 have been fully considered but they are not persuasive.
Applicant argues:
However, it is respectfully submitted that Shiomi fails to disclose the SiC semiconductor device that is presently recited in claim 1. In particular, in Shiomi's. configuration, the drift region 12 is composed of the first drift region12a, the second drift region 12b, and the third drift region 12c (see paragraph [10064] of Shiomi), and these three drift regions 12a, 12b,and 12c are formed through mutually different processes. Each layer is formed either solely by epitaxial growth or through processes including implantation of p-type impurities and implantation of n-type impurities, and therefore has a respective impurity concentration and surrounding p-type regions that are different from those of the other layers.
Specifically, first, the third drift region 12c is formed by epitaxial growth (Shiomi, [0090],S10 of Fig. 3). Next, through selective implantation of p-type and n-type impurities, the p-type first region 17b, the p-type seventh region17c, and the n-type second drift region 12b are formed (Shiomi, [0091]-[0092].S20 and S30 of FIG. 3). Thereafter, the first drift region formed through an additional epitaxial growth process (Shiomi, [0093], S40 of FIG. 3), and the p-type third region 18b is formed in the first drift region 12a by selective implantation of p-type impurity (Shiomi, [0094],S50 of IG.3).
Reply:
The drift layer is 12, which is made up of 12, 12b, 12c sublayers. Shiomi [0064].
[0064] Silicon carbide epitaxial layer 5 mainly has a drift region 12 (first impurity region 12), …… Drift region 12 has a third drift region 12c provided on buffer layer 22, a second drift region 12b provided on third drift region 12c, and a first drift region 12a provided on second drift region 12b.
Even though product-by-process claims are limited by and defined by the process, determination of patentability is based on the product itself. The patentability of a product does not depend on its method of production. If the product in the product-by-process claim is the same as or obvious from a product of the prior art, the claim is unpatentable even though the prior product was made by a different process. In re Thorpe, 777 F.2d 695, 698, 227 USPQ 964, 966 (Fed. Cir. 1985). MPEP 2113.
Applicant argues:
Zhang fails to anticipate the subject matter presently recited in the instant claims, including independent claim 10, as amended, and now independent claim 13, as amended.
In particular, claim 10 is amended to include the subject matter of claim , and now recites, inter alia, "a p-type drift region that is formed in a surface layer portion of the main surface and has an impurity concentration adjusted by a trivalent element other than boron;
wherein the drift region has an impurity concentration that is adjusted such as to increase toward the main surface."
However, it is respectfully submitted that Zhang fails to disclose the SiC semiconductor device that is presently recited in the instant claims. In particular, Zhang discloses a p-type drift region 16, and does not disclose an n-type drift region. Although Zhang may be considered to teach the p-type impurity concentration of the drift region 16, contrary to the contentions in the outstanding Office action Zhang is actually silent with respect to the type of trivalent element to be applied to the drift region 16 and with respect to any concentration gradient of the p-type impurity in the drift region 16 (see paragraphs [0040] and [0049] of Zhang).
Reply:
Claim 10 limitation recites “a p-type drift region (16/40) that is formed in a surface layer portion of the main surface and has an impurity (paragraph 42, 43) concentration adjusted by a trivalent element”. All the p-type dopants for semiconductors are trivalent elements (Boron, Aluminum, gallium)
Claim 10 language does not require an n-type drift region.
Zhang et al. teach only the use of aluminum for p-type doping (paragraphs 40 – 43).
Applicant argues:
Accordingly, it is respectfully submitted that Zhang fails to disclose a configuration in which "a p-type drift region that is formed in a layer.
Reply:
P-type drift region (16/40) is formed in layer 22/18).
Conclusion
Applicant's amendment necessitated the new ground(s) of rejection presented in this Office action. Accordingly, THIS ACTION IS MADE FINAL. See MPEP § 706.07(a). Applicant is reminded of the extension of time policy as set forth in 37 CFR 1.136(a).
A shortened statutory period for reply to this final action is set to expire THREE MONTHS from the mailing date of this action. In the event a first reply is filed within TWO MONTHS of the mailing date of this final action and the advisory action is not mailed until after the end of the THREE-MONTH shortened statutory period, then the shortened statutory period will expire on the date the advisory action is mailed, and any nonprovisional extension fee (37 CFR 1.17(a)) pursuant to 37 CFR 1.136(a) will be calculated from the mailing date of the advisory action. In no event, however, will the statutory period for reply expire later than SIX MONTHS from the mailing date of this final action.
Prior art made of record and not relied upon, considered pertinent to applicant's disclosure are listed in PTO – 892 Form.
Contact Information
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/IGWE U ANYA/Primary Examiner, Art Unit 2891
March 2, 2026